The present invention relates to a package for a microwave device used, for instance, in ground-based receivers for receiving a microwave signal transmitted from a communication satellite, broadcast satellite, etc.
Schottky-barrier-type field-effect transistors (MESFETs) employing a compound semiconductor such as GaAs are now in practical use as high-frequency FETs. Although GaAs FETs are advantageous as they have a low-noise characteristic even at extremely high frequencies such as microwave frequencies, they have a disadvantage of being prone to electrostatic breakdown compared to devices using a silicon semiconductor. Particularly in the case of low-noise amplifiers, where the noise figure is the most dominant factor, it becomes difficult to incorporate the function of a protection circuit into practical low-noise amplifiers as the addition of such a circuit may deteriorate the noise figure.
On the other hand, planar antennas are now increasingly employed as ground-based antennas for receiving a microwave signal transmitted from a communication satellite and a broadcast satellite. The planar antenna is constructed such that a large number of antenna elements are arranged on a plane and electromagnetic signals received by the respective antenna elements are collected by conductive wires. An antenna pattern is printed on a film, which is interposed between insulators. Therefore, the planar antenna is charged with much electricity.
As is understood from the above, if a receiver system employing GaAs FETs is directly connected to a planar antenna, the static electricity stored in the antenna may destruct the receiver system.
As a countermeasure against the above problem, a receiver circuit, a protection circuit and a quarter-wave line for isolating these circuits at high frequencies may be integrated on an IC chip. However, this will inevitably increase the chip size, which is disadvantageous in costs. Further, since the protection circuit is not required in many cases, an IC manufacturer needs to provide both a process for incorporating the protection circuit and a process not involving the protection circuit. Therefore, the cost reduction due to the IC mass-production effect is not expected.